A standard electronic-type torque wrench such as described in French Pat. No. 2,261,843 has a rigid elongated body having a tool end adapted to be rotationally fixed to a part to which a predetermined torque is to be applied and an opposite handle end. Transducers including strain gauges connected between the tool end and the body generate an actual-value output corresponding to the actual torque being applied by the wrench to the part rotationally coupled to the tool end. A display described in particular detail in French Pat. Nos. 2,296,835 and 2,400,996 connected to the transducers shows the actual torque. A normally button-type input device is used to generate a desired-value output corresponding to the desired torque to be applied by the wrench to the part rotationally coupled to the tool end and a comparator connected to the transducer and input means compares the actual-value and desired-value signals and generates an alarm signal when the actual torque is substantially the same as the desired torque.
Thus with this type of tool the desired torque is set by the input device, then the tool end, which is typically provided with an appropriately sized box or socket head, is fitted over the nut or bolt to be torqued down. The increasing torque applied is displayed so the user can monitor how close he or she is getting to the desired torque, and when the desired torque is reached the alarm signal, normally a beep or the like, alerts the user to stop.
Such arrangements are often fairly inconvenient when only used infrequently. To start with they must be programmed meticulously, and the display must be monitored carefully so the user is sure that the desired torque has not been improperly inputed. Similarly, after use the device must be turned off to conserve power as the battery source is typically fairly weak, and for reuse, even at the same desired torque, the system must be reprogrammed. In addition the user must normally work fairly carefully with the tool, watching the display, to avoid inadvertently going past the desired torque since at the time the alarm is given the user is usually applying considerable force to the handle end and cannot rapidly release.